Question
Speed of a boat in still water is 18 km/h while the
speed of the stream is ____ km/h. Total time taken by the boat to go 180 km upstream and 270 km downstream is ____ hours. The values given in which of the following options will fill the blanks in the same order to make the above statement true: A. 7, 27.75 B. 9, 30 C. 5, 25 D. 10, 28.5Solution
According to the question: For A: Speed of boat = 18 km/h Speed of stream = 7 km/h Speed in upstream = 18 - 7 = 11 km/h Speed in downstream = 18 + 7 = 25 km/h Total time = 180/11 + 270/25 ≈ 16.36 + 10.8 ≈ 27.16 hours So, A can't be the answer. For B: Speed of boat = 18 km/h Speed of stream = 9 km/h Speed in upstream = 18 - 9 = 9 km/h Speed in downstream = 18 + 9 = 27 km/h Total time = 180/9 + 270/27 = 20 + 10 = 30 hours So, B can be the answer. For C: Speed of boat = 18 km/h Speed of stream = 5 km/h Speed in upstream = 18 - 5 = 13 km/h Speed in downstream = 18 + 5 = 23 km/h Total time = 180/13 + 270/23 ≈ 13.85 + 11.74 ≈ 25.59 hours So, C can't be the answer. For D: Speed of boat = 18 km/h Speed of stream = 10 km/h Speed in upstream = 18 - 10 = 8 km/h Speed in downstream = 18 + 10 = 28 km/h Total time = 180/8 + 270/28 = 22.5 + 9.64 ≈ 32.14 hours So, D can't be the answer.
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